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The optimal design of production phases and ultimate pit limit for an open pit mining operation may be generated using conventional or stochastic approaches. Unlike the conventional approach, the stochastic framework accounts for expected variability and uncertainty in metal content by considering a set of equally probable realizations (models) of the orebody. This paper evaluates the performance of a new stochastic network flow approach for the development of optimal phase design and ultimate pit limit using a gold deposit as the case study. The stochastic and conventional frameworks as considered here utilize the maximum flow and Lerchs-Grossman (LG) algorithms, respectively. The LG algorithm is restricted to considering an estimated (average-type) orebody model, while the stochastic maximum flow algorithm is developed to simultaneously use a set of simulated orebody realizations as an input. The case study demonstrates that, when compared to the conventional LG algorithm as used in the industry, the stochastic approach generates a 30 per cent increase in discounted cash flow, a21 per cent larger ultimate pit limit, and about 7 per cent more metal, while it maintains a consistency in phase size.

Jan 1, 2012

Outotec?s direct leaching process is an atmospheric leaching process for sulphidic zinc concentrates. The direct leaching process, based on special leaching reactors developed by Outokumpu, is the most economical way to produce electrolytic zinc. The production scale applications of the process realized so far are in use at Boliden?s Kokkola and Odda zinc plants. A new full-scale application of Outotec?s direct leaching process will be started in 2008 in China. The process is integrated into the existing production plant, replacing part of the old production facilities by modern technology. Besides high zinc extraction the plant expansion and modernization offers also indium recovery, iron precipitation and solution purification processes. The process equipment includes tailor-made reactors designed on the basis of the work and experience of Outotec research centre. Keywords: zinc, concentrate, atmospheric leaching, technology, indium, iron precipitation, solution purification, Outotec.

Jan 1, 2008

By R. M. S. Falcon, L. M. Falcon

The prediction of the mechanical behaviour of South African coal on the basis of current proximate and other chemical parameters gives rise to problems, and the use of ultimate analyses and inferred maceral and rank analyses, although it has improved the situation to some extent, is still not satisfactory. In an attempt to reach a new level of understanding, this paper gives an in-depth review of the fundamental petrographic characteristics of coal and compares these parameters with the main types of mechanical performance. A two-tiered system of primary and secondary parameters is proposed for the prediction of coal behaviour. The primary or inherent parameters include rank and organic composition. The secondary or extraneous factors include such parameters as mineral mater, cracks or cleats, degree of oxidation, and size. In addition, an explanation is offered of several anomalous behavioural conditions in some South African coals.

Jan 1, 1987

By A. J. Duncan, Bath M. D., E. R. Rudolph

Some factors influencing gold recovery by gravity concentration by M. D. BATH,. M.A.Se. (Met.) British Columbia (Visitor) A. J. DUNCAN,. B.Sc. (Hons.) Rhodes, M.S.A.C.I. (Visitor) E. R. RUDOLPH,* M.Se. (Eng.) Rand (Member) Recent studies have shown that the overall extraction of gold from Witwatersrand ores is increased as the proportion of gold reporting to the amalgamation circuit is increased. Testwork has therefore been carried out with a view to improving recovery by gravity concentration. In this paper, the history of gold recovery by gravity concentration is reviewed, and methods and machines at present in use are briefly described. The results of plant and laboratory tests are presented, and the limitation of existing concentrators is discussed. A pilot plant is being built for the testing of improvements to the existing concentrators and of several new devices, particularly the Reichert-cone concentrator.

The optimal design of production phases and ultimate pit limit for an open pit mining operation may be generated using conventional or stochastic approaches. Unlike the conventional approach, the stochastic framework accounts for expected variability and uncertainty in metal content by considering a set of equally probable realizations (models) of the orebody. This paper evaluates the performance of a new stochastic network flow approach for the development of optimal phase design and ultimate pit limit using a gold deposit as the case study. The stochastic and conventional frameworks as considered here utilize the maximum flow and Lerchs-Grossman (LG) algorithms, respectively. The LG algorithm is restricted to considering an estimated (average-type) orebody model, while the stochastic maximum flow algorithm is developed to simultaneously use a set of simulated orebody realizations as an input. The case study demonstrates that, when compared to the conventional LG algorithm as used in the industry, the stochastic approach generates a 30 per cent increase in discounted cash flow, a 21 per cent larger ultimate pit limit, and about 7 per cent more metal, while it maintains a consistency in phase size.

Jan 1, 2012

By G. C. S. Burns

"A system has been developed to simulate the mining of the Mufulira orebody. The main output from the system is a picture-gram from which the start date and effective life of all proposed mining faces can be measured. This information provides schedule dates for the completion of major capital development projects and stope preparation activities.The orebody must be divided horizontally into main levels and vertically into blocks of equal interval. Ore reserves are defined by specifying the tonnage contained in each block and main level. Mining faces are defined by their co-ordinates, and may themselves be split into sublevels. The simulation maintains an echelon between contiguous sublevels. Other face parameters control the speed of mining, the availability and relative priority of the face.The required production from each crusher/shaft system is specified. The technique of simulating the mining process in order to achieve the required production is described."

Jan 1, 2014

By P. L. Crouse

"SynopsisFluorine – in the form of hydrofluoric acid, anhydrous hydrogen fluoride, elemental gaseous fluorine, fluoropolymers, volatile inorganic fluorides, and more – has played, and still plays, a major role in the nuclear industry. In order to enrich uranium, the metal has to be in the gaseous state. While more exotic methods are known, the standard and most cost-competitive way of achieving this is by means of uranium hexafluoride (UF6). This compound sublimates at low temperatures, and the vapour is enriched using centrifugal processes. The industrial preparation of uranium hexafluoride requires both elemental fluorine gas and anhydrous hydrogen fluoride (HF). HF is prepared by the reaction of sulphuric acid with fluorspar (CaF2). Fluorine gas in turn is prepared by the electrolysis of HF. Yellowcake is first converted to uranium tetrafluoride (UF4), using HF, after which the compound is treated with fluorine to yield UF6. After enrichment, the UF6 is reduced to UO2 for use in fuel elements in pellet form.South Africa has the largest reserves of fluorspar internationally, and is the third largest producer after Mexico and China. Fluorine technology has many associated difficulties, because of the reactivity of fluorine and the toxicity of HF. The main barriers to entry into the fluorochemical industry are thus the abilities to produce both HF and F2. Both these substances are produced locally, at the industrial scale, at Pelchem SOC Ltd. Should South Africa contemplate developing its own nuclear fuel cycle as part of the awaited new-build nuclear project, it will be imperative to leverage the existing skills with respect to fluorine technology, resident at both Pelchem and Necsa, for this purpose. This paper summarizes the fluorochemical skills developed locally over the past several decades, and suggests strategies for maintaining the technology base and developing it for the next generation of scientists and engineers.IntroductionFluorine chemistry has always had a very close relationship with the nuclear industry. Although the first mention of fluorspar was recorded in the sixteenth century, and the fundamentals had been well-developed by the Second World War, it was only during the Manhattan Project (Banks et al., 1994), when almost unlimited funds were made available for the large-scale industrialization of fluorine and related compounds, that the technology took off. Expertise in both the chemistry and the engineering aspects of fluorine is essential for the design and running of several of the unit processes in the nuclear fuel cycle."

Jan 1, 2015

By H. Zhong, S. Wang, Q. Lin

To improve the flotation performance of chalcopyrite collector, 2-(tert-butoxy)ethyl xanthate (TBEX) and its derivative O-(2-(tert-butoxy)ethyl)-N-ethyl-thionocarbamate (TBEETC) were designed and prepared by the introduction of a 2-(tert-butoxy) ethyl group into xanthate and thionocarbamate. TBEX and TBEETC were both prepared via the one-pot method with superior efficiency, which has significant commercial implications. The micro-flotation tests demonstrated that compared with sodium isobutyl xanthate (SIBX) and O-isopropyl-N-ethyl-thionocarbamate (Z-200), TBEX and TBEETC both possessed better collecting ability and selectivity for chalcopyrite. DFT calculations and XPS were utilised to investigate the flotation mechanism involving TBEX or TBEETC and chalcopyrite. The results demonstrate that although 2-(tert-butoxy) ethyl group does not interact with minerals directly, its introduction reduces the energy of HOMO, so that they can better accept electrons instead of donating electrons which leads to better interaction with copper atoms rather than iron atoms. Keywords: Chalcopyrite, flotation, thionocarbamate, xanthate, synthesis

Jan 1, 2020

By D. Wines

"Slope stability analyses have traditionally been undertaken in two dimensions assuming plane strain conditions. Although three-dimensional analysis techniques are widely available and used routinely for open pits, two-dimensional analyses are still more common due to the relative ease of model construction and the relatively rapid simulation times.Two-dimensional analyses will often produce different results to three-dimensional analyses for the same slope. It is generally thought that two-dimensional analyses will produce more conservative results. The main reason for the differences is the ability of three-dimensional analyses to account for the three-dimensional nature of the various model inputs, including the slope geometry, the distribution of soil and rock mass domains, the orientation of geological structures with respect to the excavation face, the orientation of the in situ stresses, and the distribution of pore pressure. In some cases, for a long, straight slope in basic geological conditions, two-dimensional analyses can provide a reasonable representation of the problem. However, in many cases, the inability of a two-dimensional analysis to represent the true three-dimensional nature of the problem will lead to unrealistic analysis results.This paper discusses the reasons, as detailed above, for the differences in two-dimensional and three-dimensional analysis results. Work by others is summarized, and additional numerical analyses are performed to provide an improved understanding of the effects of slope geometry, structural orientations, and in situ stresses on predicted stability. Case studies are presented for both stable and unstable slopes, and the behaviour of these slopes is related to the three-dimensional nature of the slope geometry and geology.The previous work, the new analyses performed here, and the case studies show that it is often important to provide a realistic representation of the slope in three dimensions in order to obtain reasonable stability analysis results. This is particularly true for hard rock environments where structurally controlled failure mechanisms are most likely. The paper also highlights the fact that back-analysed properties obtained from one analysis technique are not necessarily applicable to forward analyses using another technique."

Jan 1, 2016

By B. X. Huang

Hydraulic fracturing technology is presented as a solution to improve permeability and thus solve the extraction problem of coal seam gas in low-permeability gas-bearing coal seams. Given an existing group of original cracks, the propagation of main hydraulic cracks and hydraulic wing cracks was simulated using realistic failure process analysis software. The process represents the structural transformation of hydraulic fracturing and permeability improvements caused by it. In addition, a field test for improving the permeability of gassy coal seams by hydraulic fracturing was also conducted. The propagation of the main cracks and wing cracks by hydraulic fracturing forms a network of original joint cracks, hydraulic wing cracks, and main hydraulic cracks, which improve the permeability of the coal seam. High-pressure water in the drill hole and in the main hydraulic cracks permeates the two flanks of the hole, forming the permeating water pressure. With an increase in drill water pressure and an extension of the main hydraulic cracks, the permeating water pressure on both sides of the main hydraulic cracks in the coal mass also increases. Hydraulic cracks tend to form connections through rock bridges. The extension of hydraulic wing cracks through connections in the rock bridges between the cracks transforms the rock mass to a fractured structure and improves its permeability. Hydraulic fracturing technology for improving permeability in underground conditions can increase the amount of gas drainage by a factor of 15. A stress relief area develops at a radial distance of 10-2.0 m from the hydraulic fracturing drill hole, while an area of rising stresses, called the pressurized area, develops a further 15 m away from the pressurized hole. Practice has proved the existence of the stress transfer phenomenon and the high stress area after fracturing. This kind of hydraulic fracturing technology is more effective in holes drilled from underground than in surface drill holes, with respect to costs and controllability, and is therefore the major trend in gas drainage development in coal mines.

Jan 1, 2012

By Anders Erlandsson

"The crude ores from the LKAB mines are sorted and refined into a number of products. As there are a number of different plants the flow of material is often complex.in connection with studies of a proposed extensive investment program it was necessary to get a good measure of the changes which would be caused in the total profit by the different possible investments. A linear programming model was set up to accomplish this, and to cover the consequential effects on the production system. The objective function of the model maximized the total profit, taking into account restrictions in materials balances, blending conditions, production capacities and market. The changes in total profit resulting from the different investment alternatives, together with investment and fixed costs, were used in a series of investment analyses. The application has proved to be very successful and the results come very near to what was expected."

Jan 1, 2014

By Q. Zhang, X. C. Wang, S. Mao

Phosphate ore is an important strategic mineral resource in which apatite is the main valuable mineral. Flotation is the most commonly used method to separate apatite from middle-low grade phosphate rock. Selective flotation separation is based on the difference of physical and chemical properties of minerals occurring at the three interfaces of mineral/bubble/water. Surface and interface chemistry of mineral have been playing an important role in interpreting and governing its flotation phenomenon. In-situ, visualized and high-precision analytical techniques, such as Time-of-Flight Secondary Ion Mass Spectrometry, Atomic Force Microscopy and Molecular Simulation, have been applied to explore and uncover microscopic nature of apatite flotation. Consequently, a great progress at molecular or atomic level on surface and interface chemistry of apatite flotation has achieved in the past decades. In this paper, the research progress of surface and interface chemistry of apatite flotation such as surface wettability, surface-charging characteristics, surface dissolution behavior, adsorption mechanisms of fatty acid collector and depressor on apatite surface were systematically reviewed. This review will be helpful for the development of more selective reagents and efficient technologies for apatite flotation. Keywords: Apatite, Flotation, Surface and interface chemistry, Surface analysis technology

Jan 1, 2020

By G. T. van Rooyen

In this overview of materials engineering, the author, drawing on his long experience from his student days until the present (emeritus professorship), briefly recounts the main developments in this field: dislocation theory, fracture problems, and the development of alternative materials such as ceramics and polymers. He then takes a look at the future, in which he foresees a greater demand for materials engineers, and leading roles for universities and technikons in collaboration with industry.

Jan 1, 1996

By M. M. Bwalya, F. K. Mulenga

"SynopsisThe application of the attainable region (AR) technique to the analysis of ball milling is currently limited to batch data. This paper introduces the use of the technique to continuous milling.To this end, an industrial open milling circuit processing a platinum ore was surveyed. Samples were collected and later characterized by means of laboratory batch testing. On site, several milling parameters were varied systematically so as to collect data for modelling purposes. These paramters included ball filling, slurry concentration, and feed flow rate. After data analysis, a simulation model of the open milling circuit was developed under MODSIM®, a modular simulator for mineral processing operations. The mill was then simulated and the data generated was analysed within the AR framework.Initial findings reveal an opportunity to gain valuable insight by studying milling using the AR technique. From an exploratory perspective and inasmuch as this study is concerned, feed flow rate, ball size, and ball filling were identified as being pivotal for the optimization of open ballmilling circuits. Mill speed, on the other hand, had only a limited effect on the production of particles in the size range -75 +10 µm.IntroductionGlasser and Hildebrandt (1997) propounded the attainable region (AR) as a technique for the analysis of chemical engineering reactor systems. Results have since been produced and tested on both the laboratory and pilot scales. The method results in a graphical description of chemical reactions by considering the fundamental processes taking place in the system, rather than the equipment. From the plotted graphs, the process and the reactors can be synthesized optimally into a flow sheet.The use of the AR method still has a long way to go as far as mineral processing is concerned. For instance, several articles have reported the application of the AR technique to ball milling: Khumalo et al. (2006, 2007, 2008); Khumalo (2007); Metzger et al. (2009, 2012); Metzger (2011); Katubilwa et al. (2011); Hlabangana et al. (2012). Their main shortcoming has been the exclusive use of laboratory batch grinding data.To address this deficiency, Mulenga and Chimwani (2013) proposed a way by which the technique could be extended to continuous milling. In effect, the batch milling characteristics of a platinum-bearing ore (Chimwani et al., 2013) were used and scaled up to an open milling circuit. Then, with simplifying assumptions, an attempt was made to optimize the residence time of particles inside the mill. Later, Chimwani et al. (2014a) presented some optimization examples involving various milling parameters. The sequence of published articles then paved the way for the study of industrial milling systems with the AR methodology."

Jan 1, 2015

By N Morales, G Nelis

Short-term plans must meet the long-term goals while accounting for shovel selectivity, operational space, and scheduling restrictions. There are several approaches that deal with these issues to deliver a feasible short-term schedule. This paper compares two approaches based on mathematical programming to address the short-term mining cut definition and scheduling in an integrated way. They work by scheduling extraction to comply with long-term production goals, but they differ in how mining cuts are modelled. The first approach schedules Selective Mining Units (SMUs) but aggregates them around predefined locations. The second approach does not work on SMUs; it decides directly what mining cuts are to be used from a pre-defined set of shapes. It assigns a destination and schedules the extraction for the selected mining cuts. We applied both approaches in a real case study to compare their results in terms of profit, mining cut design, expertise needed, profit, and optimisation performance.

Sep 1, 2021

By B. Yu, M-H. Cao, C. Zhou, X-Z. Zhang

The transient infiltration and lubrication behaviour of slag during continuous casting of steel is important for billet quality. A two-dimensional coupled mathematical mould model was developed to investigate these phenomena. The accuracy of the model was verified by comparing the calculated slag consumption with measurements by the plant. The results show that the liquid slag is consumed from the middle and late period of positive strip time to the next early period of positive strip time, including the entire negative strip time. The maximum downward infiltration velocity and positive pressure in the slag channel is at the middle of the negative strip time. Increasing the positive pressure of the slag channel is conducive to lubrication. The shear stresses acting on the shell surface and at the mould side were determined by the lubrication slag consumption and total slag consumption, respectively, and gradually decreased with increasing slag consumption. The negative strip time was lengthened to increase the slag consumption and prolong the time near the maximum downward shear stress, so as to be conducive to the demould.

Apr 16, 2024

By F. P. Agterberg, A. G. Fabbri

"A statistical analysis was done on the locations of 718 copper and 1 257 gold deposits in Abitibi. This area of about 20 000 square miles is one of the better-explored metal-producing areas of Canada.Patterns of clusters were studied by harmonic analysis. Several two-dimensional power spectra showed a number of distinct peaks. Sets of crest lines for patterns of interfering waves were constructed on the basis of these peaks. They pass through elongated clusters of deposits which are spaced more or less equally. For copper these periodic regularities in location may coincide with geological structures largely of Archean age (major fractures and sedimentary belts indicating synclinal structures). A directional relationship with swarms of diabase dykes of known ages and distinct attitudes indicates that the gold mineralization is, in part, younger than the copper mineralization."

Jan 1, 2014

By Z. Levinson, R. Dimitrakopoulos

A mining complex is an engineering system where raw materials are extracted from several mines, processed, transported, and sold to the market. The uncertainty and local variability of material grades and their locations within the related mineral deposits are critical for determining the optimal life-of-mine extraction sequence, destination policy, operating modes, and capital investment decisions, which define the production schedule of a mining complex. Infill drilling is used to further characterise a mineral deposit and reveals information that changes the representation of the resource model and potentially the resulting optimal long-term production schedule. A self-learning reinforcement learning approach is proposed to determine the optimal drilling locations that maximise the net-present value of the long-term production schedule and the associated financial forecasts by adapting the schedule to additional information. A case study at a copper mining complex demonstrates a $70 M increase in project value by collecting drilling information with a $1 M budget.

Sep 1, 2021

By J. T. M. Amphlett, C. A. Sharrad, M. D. Ogden, R. I. Foster

"A renewed interest in nuclear power around the world in order to reduce greenhouse gas emissions is going to increase demand for uranium as fuel. This will result in more uranium being mined, which will in turn increase associated environmental pressures, such as fresh water use. A move to lower quality waters containing impurities such as chloride would help alleviate these pressures. In this work, we determined the uptake characteristics of weakly basic anion exchange resin Ps-EDA towards uranium from saline solutions in a dynamic flow column. Breakthrough curves were produced, with suppression of uptake being observed for chloride concentrations above 5 g L-1. Calculated resin saturation capacities at zero and 5 g L-1 chloride are comparable with literature values for strong-base anion exchange resins, and exceed those published for weak-base resins up to 20 g L-1 chloride. Data has been fitted to multiple breakthrough models, with the modified dose-response model most effectively predicting uranium recovery. The results show that the ethylenediamine functionality could be suitable for use in future uranium processing flow sheets where a high-saline lixiviant is used. IntroductionIon exchange (IX) is a key technology in the uranium mining industry and is well established for the extraction of uranium from both acidic and alkaline leach liquors (Edwards and Oliver, 2000). It was first employed in 1952 at the West Rand mine in South Africa (Ford, 1993; Taylor, 2016). H2SO4 and Na2CO3 are the most commonly employed lixiviants used to solubilize uranium in acidic and alkaline leach conditions respectively. The chemistry of these systems causes uranium to form anionic sulphate or carbonate complexes, which can be taken advantage of by anion exchange resins.Another major technology for the extraction and purification of uranium from leach liquors is solvent extraction (SX). This technique involves the extraction of uranium from the aqueous phase into an immiscible organic layer. Although this is a commonly used method, there are major drawbacks to it, including the use of large volumes of flammable solvents, solvent loss, phase disengagement, third phase formation, and the production of problematic degradation products (Veliscek-Carolan, 2016). These problems can be circumvented through the use of IX resins."

Dec 1, 2018

By F. T. Cawood

This paper reviews the Mineral and Petroleum Resources Royalty Bill of 2006, identifies potential areas that require further consideration by the National Treasury and, where appropriate, offers alternatives. At its basic level a royalty regime consists of two elements: the base and the rate that must be applied to the base. Deciding on an acceptable royalty rate is a complex matter and can be done only after extensive analysis of all variables affecting the competitiveness of the regime. The proposed royalty rates are in the range of zero to five per cent and are based on sales revenue. It is argued that future investment patterns are more likely to be influenced by market cycles and commodity prices than policy events. Inevitably the current boom in the minerals sector will come to an end and the success of the proposed regime will be known only when profit margins are under pressure. Policy makers must therefore have the long run in mind when developing policies that affect the ability of industry to do business, without the need to renegotiate each time there is a change in the market. A long-run policy must be sufficiently flexible to allow for consistently fair sharing ratios and splitting of revenues between government and industry. Although broadly in line with international practice, the current version cannot be regarded as internationally competitive and efficient. In order for the royalty bill to become internationally competitive, promote beneficiation of mineral production and adequately compensate the State for the loss of a national resource, the National Treasury should heed the following main recommendations in this review: 1. Abandon the notion that each mineral product must have its own royalty rate; 2. Introduce an NSR type royalty that allows for value-addition costs to be deducted from the base; and 3. Provide for automatic relief through the use of a sliding-scale mechanism based on ability to pay, e.g. the X-Factor used in the gold mining tax formula.

Jan 1, 2007